This application is in response to PAS-10-151 {Grants for Alzheimer's Disease Drug Discovery (R21)}. Novel vehicles are needed to effectively target direct delivery of immunotherapeutics to the brain in order to maximize the efficacy of passive immunization for treating, delaying or preventing Alzheimer's disease (AD), a disease that currently afflicts >5 million Americans. Conjugation of the lectin, Wheat Germ Agglutinin (WGA), has been shown to enhance intranasal uptake of candidate drugs and promote direct delivery to brain via (i) Adsorptive or receptor-mediated endocytosis into the olfactory sensory neurons (OSN) followed by intracellular transport to olfactory bulb; (ii) Non-specific fluid phase endocytosis into the OSNs followed by intracellular transport to olfactory bulb; and/or (iii) Extracellular diffusion along the inter-olfactory epithelial clefts directly to the olfactory bulb and/or CSF. Passive immunization by intravenous injection of Ass monoclonal antibodies (mAb) has shown promising results such as lowering of cerebral Ass and stabilization or prevention of cognitive deficits in preclinical studies in transgenic mouse models of AD and in early human clinical trials. However, the level of antibody penetration in the brain is limited by the blood-brain-barrier (BBB). In addition, in mice and humans with vascular amyloid, high levels of anti-Ass antibodies in blood has led to microhemorrhage and vasogenic edema. This project aims to overcome such limitations by maximizing the efficacy of the intranasal route of anti-Ass antibody delivery using a WGA carrier protein. This project will test the efficacy of WGA as a novel vehicle that will not only enhance delivery of anti-Ass mAb, 3A1, that binds to mono/dimers and fibrillar Ass (To be provided by Dr. Lemere-Consultant) by virtue of its endocytic uptake preference, but will also facilitate passive diffusion of 3A1 due to its nasal mucosa-like biochemical composition, maximizing immunotherapeutic efficacy of intranasal passive immunization, to be tested in Alzheimer's 5XFAD model. Hypothesis: Intranasal delivery of WGA-conjugated 3A1 mAb combined with unlabeled 3A1 antibody will maximize the immunotherapeutic potential of intranasal passive immunization ameliorating AD-like patho-cognitive changes in 5XFAD transgenic mice. Specific Aims: [1] Trafficking of WGA-3A1 antibody after intranasal delivery to the brain in wild type mice and binding of 3A1-WGA to Ass plaques in the brains of 5XFAD mice and human AD. [2] Determining if intranasal passive immunization with WGA-conjugated 3A1 mAb combined with unlabeled 3A1 antibody will prevent AD-like patho-cognitive changes in young pre-plaque 5XFAD mice. [3] Determining if intranasal passive immunization with WGA-conjugated 3A1 mAB combined with unlabeled 3A1 antibody will attenuate AD-like patho-cognitive changes in old late-stage plaque-bearing 5XFAD mice. All resources, including transgenic mice, and required expertise are ready to begin this study. Significance: This project will evaluate a novel delivery system to target immunotherapeutics directly to the brain, and thus advance one of the most promising therapies for delaying the progression or prevention of AD.